发表机构
Pontificia Universidad Católica de Chile; Las Campanas Observatory, Carnegie Science; University of California Santa Barbara; Instituto de Astrofísica de la Facultad de Ingeniería y Ciencias, Universidad Diego Portales; Texas A&M University; George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University; Caltech/IPAC; Institute for Cosmic Ray Research, The University of Tokyo; Space Telescope Science Institute（智利天主教 Pontificia 大学; 拉斯坎帕纳斯天文台，卡内基科学; 加州大学圣塔芭芭拉分校; 迭戈·波特莱斯大学工程与科学学院天体物理研究所; 德克萨斯农工大学; 德克萨斯农工大学乔治·P和辛西娅·伍兹基础物理与天文学研究所; 加州理工学院/IPAC; 东京大学宇宙射线研究所; 太空望远镜科学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究利用JWST直接Te法测量z≈6.93原星系团中LAEs的金属丰度，发现其高于一般LAEs但低于MZR，揭示过密度驱动加速组装与原始气体流入的复杂作用。
AI 中文摘要
背景。再电离时期的原星系团被认为承载了相当大比例的宇宙恒星形成率密度，这使得它们对再电离的时间和拓扑结构至关重要。气体相位金属丰度是星系演化阶段的关键示踪剂，现在可以通过JWST在早期宇宙中直接测量。目的。我们通过直接（基于Te的）方法，利用[O III]λ4363极光谱线，测量了z≈6.93处LAGER-z7OD1原星系团中Lyman-α发射体（LAEs）的气体相位金属丰度，并将其与恒星质量相结合，以约束高密度环境中的质量-金属丰度关系（MZR）。方法。我们使用JWST/NIRSpec MSA G395H光谱，通过自洽的解析公式推导金属丰度，并基于观测到的巴耳末减缩，通过蒙特卡洛模拟将尘埃消光不确定性传播到不对称误差预算中。恒星质量来自对JWST/NIRCam和UltraVISTA测光数据的BEAGLE SED拟合。结果。我们获得了五个可靠的[O III]λ4363探测和一个上限，12+log(O/H) ≈ 7.2-8.0。加权光谱叠加得到12+log(O/H) = 7.76^{+0.06}_{-0.05}，比JWST巡天中类似红移的LAEs叠加结果高约0.26 dex。然而，MZR拟合给出的斜率γ = 0.232 ± 0.214，归一化Z_0 = 7.888 ± 0.199，使我们的源位于z~5-7处正常星系和近期原星系团基准的既定MZR之下。结论。相对于一般LAEs更高的金属丰度表明由过密度驱动的加速组装，而低于MZR的偏移则指向质量增长与气体吸积之间的复杂相互作用。由于我们针对的是活跃恒星形成的LAEs，我们很可能捕捉到了来自星系际介质的原始气体流入阶段，这种流入为恒星形成提供燃料，但稀释了这些原星系团成员的星际介质。
英文摘要
Context. Protoclusters at reionization are thought to host a significant fraction of the cosmic star formation rate density, making them crucial for the timing and topology of reionization. The gas-phase metallicity, a key tracer of galaxy evolutionary stage, can now be measured directly in the early Universe with JWST. Aims. We measure the gas-phase metallicity of Lyman-$α$ emitters (LAEs) in the LAGER-z7OD1 protocluster at $z\approx6.93$ via the direct ($T_e$-based) method using the [O III]$λ$4363 auroral line, and combine it with stellar masses to constrain the mass-metallicity relation (MZR) in dense environments. Methods. We use JWST/NIRSpec MSA G395H spectroscopy, derive metallicities with self-consistent analytic prescriptions, and propagate the dust-extinction uncertainty into an asymmetric error budget via Monte Carlo simulations based on the observed Balmer decrements. Stellar masses come from BEAGLE SED fitting of JWST/NIRCam and UltraVISTA photometry. Results. We obtain five secure [O III]$λ$4363 detections and one upper limit, with 12+log(O/H) $\approx$ 7.2-8.0. The weighted spectral stack yields 12+log(O/H) = $7.76^{+0.06}_{-0.05}$, ~0.26 dex higher than stacks of LAEs at similar redshifts from JWST surveys. However, the MZR fit gives a slope $γ$ = 0.232 +/- 0.214 and normalization $Z_0$ = 7.888 +/- 0.199, placing our sources below the established MZR of normal galaxies and recent protocluster baselines at $z\sim5-7$. Conclusions. The higher metallicity relative to general LAEs suggests accelerated assembly driven by the overdensity, while the offset below the MZR points to a complex interplay between mass build-up and gas accretion. Since we target actively star-forming LAEs, we are likely capturing a phase of pristine gas inflow from the intergalactic medium that fuels star formation but dilutes the interstellar media of these protocluster members.
Comments9 pages
